1. Technical Field
The invention relates generally to fuel injected, two-stroke engines and more particularly to throttle position sensors for use with fuel injected, two-stroke engines.
2. Related Prior Art
Attention is directed to the following prior art references:
______________________________________ 5,065,723 Broughton et al. November 19, 1991 5,062,403 Breckenfeld et al. November 5, 1991 4,981,127 Morikawa January 1, 1991 4,932,371 Albertson et al. June 12, 1990 4,895,120 Tobinaga et al. January 23, 1990 4,864,996 Hensel September 12, 1988 4,843,555 Hattori et al. June 27, 1989 4,747,381 Baltz et al. May 31, 1988 4,745,901 Reifenberger et al. May 24, 1988 4,729,358 Morita et al. March 8, 1988 4,643,149 Dunham et al. February 17, 1987 4,524,745 Tominari et al. June 25, 1985 ______________________________________
The speed-load cycle under which a carbureted, two-stroke outboard motor operates entails a specific relationship between the boat operator's speed request, the engine ignition timing and throttle plate position. At low engine speeds, engine control is accomplished primarily through advancing or retarding the engine's ignition timing rather than through control of air flow to the engine by movement of the throttle plate.
At higher engine speeds, engine control is accomplished primarily through movement of the throttle plate with little change in the timing of the engine's ignition. For example, if the boat operator moves the remote control lever from an idle position to a 25% power position, the operator indicates that engine speed is to increase to approximately 25% of full speed. An increase in engine speed from idle to 25% of full speed is typically primarily accomplished through an advance in ignition timing of approximately 12.degree. and only a slight opening of the throttle plate. Further advance of the remote throttle control lever from 25% to 100%, or wide open throttle, has little effect upon ignition timing, which is typically already fully advanced at 25% throttle, but moves the throttle plate from a slightly opened position to a fully opened position. These relationships between the boat operator's speed requests, ignition timing, and throttle plate position are well known and desirable. These relationships are normally accomplished in carbureted, two-stroke engines through a series of mechanical linkages and cams.
A fuel-injected, two-stroke outboard motor is generally known to use an electronic control unit to control engine operation. On some fuel injected, two-stroke engines, two of the primary input signals used by the electronic engine control unit for controlling the engine's ignition timing, its fuel injectors and other components are input signals indicating the operator's speed request and the engine's speed. To provide such an input signal indicating the operator's signal request, it is known to locate a sensor on the engine's throttle plate. It is also known to provide a sensor on the remotely located operator control member itself to provide a signal indicating the position of the operator control member. U.S. Pat. No. 4,932,371 shows such an arrangement including a sensor located on an accelerator pedal located remotely f rom the engine.